The present invention relates to an optical system capable of achieving a line of sight with a specific point and including a measuring device for detecting the angular deviation of a radiation source from a line of sight with the point.
The invention is particularly intended to be used when determining the angular deviation of a remote object from the line of sight of an object or target to be tracked. In such cases the optical system is usually directed towards a point on the object to be followed. If the object whose angular deviation is to be determined, emits radiation, the angular deviation of the radiation source from the line of sight to the object can be determined by a measuring device. The radiation can be generated by a radiation source located within a housing of the remote object, or it can be generated by its propulsion motor, in which case the transmitted radiation takes the form of an infrared radiation. The radiation may also, however, be derived from reflector arranged on the remote object. In such a case the radiation is transmitted towards the remote object from a radiation source located at the site of the optical system.
A particularly interesting and advantageous application for the present invention is in combination with an optical sight of the type comprising a tracking telescope with cross hairs or other visual sight reference symbols employed to point at and follow a target, and a measuring device which collects the radiation emitted by a moving object and determines the deviation of the object from the line of sight with the target.
It is previously known in the art to provide the measuring device with a movable measuring mask located in an image plane of an optical system so that the radiation emitted by the radiation source alternatingly passes through the mask and is prevented from penetrating the mask.
The movable mask may consist of a glass surface having a coating layer superimposed thereon. The layer may take a form such that information regarding the position of the radiation source can be derived from the relation between the occuring fluctuations of the radiation and the angular position of the measuring mask.
It is also previously known to employ an optical system having a tracking telescope comprising an objective lens, ocular and a sighting symbol, along with some type of cross hairs comprising thin lines on a glass surface located in the image plane of the objective. By means of the ocular, it is possible for the operator to view the target and its background and by means of control knobs etc, it is possible for the operator to point and maintain the symbol in line of sight with the target during the target tracking operation.
Because of the fact that two different main functions, ie. aiming and position measuring, have to be effectuated, it has up until now been necessary to use two different optical systems, ie an optical system for aiming and an optical system for measuring the position of the object. In order to attain an acceptable accuracy in the measuring operation, it is important that the relative position of the measuring and the aiming devices, respectively, is not influenced by mechanical deformations, temperature changes etc. A disturbance of an optical or mechanical element may cause a change of the relative position of the two optical systems making up the sighting system. As a result measuring systems are, in order to obtain an acceptable measuring accuracy, generally provided with means to control and adjust the line of sight of the telescope and the axes of the measuring device.